1. Field
The present disclosure relates to an internal combustion engine and a controller for the internal combustion engine.
2. Description of the Related Art
A known internal combustion engine having a power turbine device and a turbo charger device and a controller for the internal combustion engine are described in Japanese Patent No. 4892054. The exhaust system of the internal combustion engine has an exhaust passage, a bypass passage, and a shortcut passage, with a supercharging turbine of a turbo charger device provided at some midpoint of the exhaust passage. The bypass passage, which is used for bypassing the supercharging turbine in the exhaust passage, branches off from the exhaust passage at a point upstream of the supercharging turbine and subsequently merges at a point in the exhaust passage downstream of the supercharging turbine.
An upstream flap is provided at the point where the bypass passage branches off and is configured to be switchable between a state in which the entrance to the exhaust passage on the supercharging turbine side is closed, a state in which the entrance to the bypass passage is closed, and a state in which both the entrances are opened.
The power turbine device includes a rotary machine and a power turbine which is coupled to the rotating shaft of the rotary machine and located at some midpoint of the bypass passage. The shortcut passage branches off from the bypass passage at a point upstream of the power turbine and subsequently merges with the exhaust passage at a point slightly downstream of the supercharging turbine. A downstream flap is provided at the point where the shortcut passage merges and is configured to be switchable between a state in which the exit of the shortcut passage is opened with the exhaust passage downstream of the supercharging turbine closed and a state in which the exhaust passage is opened with the exit of the shortcut passage closed.
With this controller, during high-load, high-revolution operation of the internal combustion engine, the upstream flap is driven so as to open both the entrance of the exhaust passage on the supercharging turbine side and the entrance of the bypass passage, while the downstream flap is driven so as to open the exhaust passage with the exit of the shortcut passage closed, as illustrated in FIG. 2 of Japanese Patent No. 4892054. This directs exhaust gas from an exhaust manifold to both the supercharging turbine side and the power turbine side, and after passing through them, the two flows of exhaust gas meet at the merging point of the bypass passage and the exhaust passage and further flows down the exhaust passage.
During this process, the thermal energy of the exhaust gas is transformed into kinetic energy when it passes through the supercharging turbine to be utilized for supercharging action of the turbo charger device. When charging of a battery is possible, the thermal energy is transformed into kinetic energy when it passes through the power turbine and the kinetic energy is converted to electric power through regenerative control on the rotary machine to be stored in the battery.
In a cold start of the internal combustion engine, the upstream flap is driven so that the entrance to the bypass passage is opened with the entrance to the exhaust passage on the supercharging turbine side closed and the downstream flap is driven so that the exhaust passage is closed, as illustrated in FIG. 3 of Japanese Patent No. 4892054. This directs the exhaust gas from the exhaust manifold only to the power turbine. Then, in order to suction secondary air into the exhaust manifold, a negative pressure is produced in the exhaust passage downstream of the exhaust manifold through powering control of the rotary machine.